AD30 and AD55 Underground Articulated Trucks Power Train Electronic Control System Caterpillar

Illustration 1	g00772309
Schematic of the front service brake and retarder pressure switch

This diagnostic code is associated with the front service brake and retarder pressure switch. This diagnostic code is recorded when the Power Train/Chassis Electronic Control Module (ECM) reads the voltage of the switch as being above normal.

The possible causes of this diagnostic code are listed:

• There is an open in (wire 202-BK(Black)). The open is between the switch and frame ground.

• The switch has failed.

• (Wire H762-PU(Purple)) is open between the switch and the ECM.

• The ECM has failed. This is unlikely.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear these diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 1496 FMI 03 is active before performing this procedure.

Note: Use the 146-4080 Digital Multimeter for the measurements in this procedure.

System Response:

Before the ECM determines that a diagnostic code exists, the machine will be difficult to upshift. The ECM will default to the shift points for the retarding shift map. When the ECM determines that a diagnostic code exists, the ECM will default to the shift points for the non-retarding shift map.

Test Step 1. CHECK THE SWITCH.

1. Turn the battery disconnect switch and the key start switch to the ON position.

2. Ensure that the diagnostic code is active.

3. Access the Caterpillar Electronic Technician (ET). View the display that is shown for the switch. For more information about the ET, see Systems Operation, Troubleshooting, Testing and Adjusting, "Service Tools".

4. Cycle the switch.

Expected Result:

The diagnostic code changes from being active to being not active as the switch is cycled.

Results:

• OK - The diagnostic code is active. Then, the diagnostic code is not active as the switch is cycled. The switch is failed.

  Repair: Repeat this test "CHECK THE SWITCH" in order to verify that the switch has failed. Replace the switch.

  STOP

• NOT OK - The diagnostic code remains active. The diagnostic code does not change. The machine harness has failed or the ECM has failed. Proceed to Test Step 2.

Test Step 2. CHECK FOR AN OPEN CIRCUIT.

1. Install a jumper wire between the signal (wire H762-PU(Purple)) and the frame ground (wire 202-BK(Black)) at the switch.

2. Turn the key start switch and the battery disconnect switch to the OFF position.

3. Disconnect the J1 and J2 machine harness connectors from the ECM.

4. At the J1 machine harness connector for the ECM, measure the resistance from contact J1-20 (wire H762-PU(Purple)) to frame ground.

Expected Result:

The resistance that is measured is less than 5 ohms.

Results:

• OK - The resistance that is measured is less than 5 ohms. Proceed to Test Step 3.

• NOT OK - The resistance measurement is not less than 5 ohms. There is an open in the machine harness. The open circuit is in (wire H762-PU(Purple)) or (wire 202-BK(Black)).

  Repair: Repair the machine harness or replace the machine harness. Verify that the diagnostic code is no longer active.

  STOP

Test Step 3. CHECK FOR A SHORT TO THE +BATTERY CIRCUIT.

1. The key start switch and the battery disconnect switch remain in the OFF position.

2. Remove all jumper wires that were previously installed.

3. The J1 and J2 machine harness connectors remain disconnected from the ECM.

4. At the J1 machine harness connector for the ECM, measure the resistance from the signal contact J1-20 (wire H762-PU(Purple)) to all possible sources of +battery.

Expected Result:

The resistance for each measurement should be greater than 5 ohms.

Results:

• OK - Each resistance measurement is greater than 5 ohms. The harness is correct. The ECM has failed. Proceed to Test Step 4.

• NOT OK - Each resistance measurement is not greater than 5 ohms. The machine harness has failed.

  Repair: There is a short in the machine harness. The short is between the signal (wire H762-PU(Purple)) and the wire with the low resistance measurement. Repair the machine harness or replace the machine harness.

  STOP

Test Step 4. CHECK IF THE DIAGNOSTIC CODE REMAINS

1. Inspect the contacts of the harness connectors and clean the harness connectors.

2. Reconnect all the harness connectors.

3. Turn the battery disconnect switch and the key start switch to the ON position.

4. Operate the machine.

5. Check the status of the CID 1496 FMI 03.

Expected Result:

The CID 1496 FMI 03 is active.

Results:

• YES - The CID 1496 FMI 03 is active. The diagnostic code has not been corrected. The ECM may have failed.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. Refer to Systems operation, Troubleshooting, Testing and Adjusting, "Electronic Control Module (ECM) - Replace" for the machine that is being serviced.

  STOP

• NO - The CID 1496 FMI 03 is not active. The diagnostic code does not exist at this time.

  Repair: The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation.

  STOP